Why trees in the cities need protecting

by Margo White / 25 February, 2018

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Pōhutukawa trees.

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Why trees are vital to New Zealand's cities

Cities are losing their big trees at an alarming rate. At what cost to our health and wellbeing?

I live in a small house in a suburb that wouldn’t be described as leafy, but it has a lot of trees, most of them in people’s yards. This includes a massive pōhutukawa on the front lawn of the house next door, which as I write this, is filling the frame of my living-room window with a blowsy blaze of vermillion flowers.

My small house feels bigger, thanks to its view of what is the biggest tree in the street and, when it’s in bloom, the most spectacular. It was planted, my neighbours tell me, the year I was born half a century ago, as a 10cm sapling the neighbours had bought for a shilling off an entrepreneurial boy across the road who was cultivating pōhutukawa as a way to make a buck.

I’m grateful for that tree; it’s such a show-off it sometimes makes me laugh out loud. But I’ve started to worry about its future. There’s myrtle rust to think about. Also, the neighbours are getting on and they have a large section. If they sell up, the house will likely go to someone who’ll chop down the pōhutukawa to make way for another house. All over Auckland trees are being chopped down to make way for houses, another driveway, another storm-water pipe, to open up someone’s view or to liberate them from the need to clean up the leaves. People are talking about the Great Chainsaw Massacre.

In the age of global warming, kauri dieback disease and now myrtle rust, this is one of the environmental legacies of the former National government. More specifically, the Resource Management [Simplifying and Streamlining] Amendment Act 2009, which came into effect in 2012, removing blanket tree protection and limiting the ability of councils to protect trees in their city or region.

The government said this would reduce the costs caused by the large number of resource consents required due to blanket tree protection rules in urban environments. It also left councils throughout the country scrambling to find alternative legislative ways to protect trees. The Act framed trees as just another property right (My Home, My Tree), rather than a community asset in need of protection – which, in the age of global warming, strikes me as individualism gone mad. 

Trees don’t just stand there, looking pretty. Considering things from a purely anthropocentric perspective, they protect us from the harsh UV rays of the sun; absorb noise; mitigate flooding (apparently we’re going to get more of that); filter our polluted air and water; sequester carbon dioxide, a greenhouse gas that makes the planet warmer; and so on. The bigger the tree, the better – a typical 20m-tall street tree may provide three to seven times the environmental benefit of one that is 10m high.

Yet people are chopping them down. The Tree Council, an advocacy group for Auckland’s trees, has estimated the city has lost 30% of its trees since the Act came into effect five years ago. This figure, based on anecdotal evidence gathered from arborists and members of the public as well as from resource consent applications, could be disputed, but it’s probably not far-fetched.

“I would say that we have lost a lot,” agrees Dr Margaret Stanley, an ecologist at the University of Auckland. Stanley co-authored a study that showed that the Auckland isthmus has just six percent of its urban forest left, and 63 percent of that is on private land.

Some of the trees on private land are protected if they’re listed on the district plan under the Schedule of Notable Trees (SoNT). According to Stanley, this amounts to 15% of what was previously protected in Auckland. And that protection can be removed by resource consent anyway — the Tree Council claims requests to get rid of a protected tree are almost always approved.

We should have a firm idea of what we’re losing soon. Auckland Council is expected to release LiDAR (Light Detection and Ranging) data in early 2018, which will compare information from 2017 to data gathered before the Act came into effect. It’s not looking good. “You can just look at the aerial photos and see the difference,” says Stanley.

Stanley estimates some 7000 trees are protected under the SoNT in Auckland. By my calculation, that amounts to 0.005 protected trees per person. She also notes that most of them are in the leafy, older, more expensive suburbs in central Auckland, with few in South Auckland.

Trees are a class issue. Or, put another way, environmental inequality is a serious social issue. A study done in the US, involving low-income African-American children from public housing projects, found children living in apartment buildings that had views of trees and/or a bit of green space, had superior attention capacities and impulse control than similar children living in those that didn’t. (The residents had been randomly assigned an apartment, so the difference couldn’t be put down to differences in income.) 

The same researchers looked at the relationship between vegetation and crime in an inner-city, 98-apartment block in Chicago, and found there were fewer reported crimes committed by those living in apartments with views of or access to trees. Yes, of course reducing crime depends on addressing the complex factors underlying crime rather than planting trees, but the study suggested “in barren, inner-city neighbourhoods, planting a few trees may work to inhibit crime, creating safer neighbourhoods for poor families and their children”.

For evidence of the influence of trees on physiological human health, consider the impact of the emerald ash borer, which resulted in the deaths of millions of trees in North America and, it seems, quite a few people. One study looked at disease rates in 15 states from 1990 to 2007, and suggested the borer was associated with 6113 human deaths from respiratory illness and 15,080 deaths from heart disease in that period. Another study published in Scientific Reports in 2014, led by University of Chicago assistant professor of psychology Marc Berman, showed an additional 10 trees on a given block corresponded to a 1% increase in how healthy nearby residents felt. Berman said: “To get an equivalent increase [in perceived health] with money, you’d have to give each household in that neighbourhood $10,000 dollars – or make people seven years younger.”

Trees on public land are largely protected, but they’re vulnerable too. If you Google “poisoning of pōhutukawa”, you’ll find countless examples of people taking things into their own hands in various parts of the country, for their own mad, selfish and possibly sociopathic reasons. In November 2017, it was reported that a stand of six large pōhutukawa trees had to be cut down on the Kāpiti Coast, north of Wellington, after being poisoned by a herbicide so potent nothing could be planted in the public park for up to a year.

And it was only thanks to the efforts of community group the “Pōhutukawa Savers” that Auckland Transport was stopped from cutting down six 80-year-old pōhutukawa along a busy Auckland road, mainly to make way for an extra turning lane. As group members wrote in defence of the trees: “They’re heritage specimens on public open space in our collective backyard.”

Quite – and the trees in other people’s yards could also be seen as part of the collective backyard. With all our 21st-century technological know-how, humans haven’t yet developed a technology that can do half of what trees do for the environment and for us – certainly not a technology that stands there quietly, sometimes rustling or waving in the wind, looking pretty. Where there’s a will to live, there are, I bet, trees.

This was published in the February 2018 issue of North & South.


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